Control system for earth moving machine



Oct. 16, 1962 F. J. OCNASCHEK CONTROL SYSTEM FOR EARTH MOVING MACHINE 3 Sheets-Sheet 1 Filed March 2. 1960 k we L WM 5 1 Mn T m "Wm NM 0 Z a u. x 4 3 R A; R \M W M 4 5w m D M A E N 5 MW L E In nwa w m F 5 r6 m 2 3/|\ 3 w w L a N r 7 KW? m6 2 M fi an v x g --\6 i [9 32 PM 6 OF M YMORF n mafia I .TYOE m m m M V S 7 A AT-roRMe-rs Oct. 16, 1962 F. J. OCNASCHEK 3,058,242

CONTROL SYSTEM FOR EARTH MOVING MACHINE Fil'ed March 2, 1960 5 Sheets-Sheet 2 Va; 774 6-: R0 PRoPoR nomu.

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Oct. 16, 1962 F. J. OCNASCHEK CONTROL SYSTEM FOR EARTH MOVING MACHINE 5 Sheets-Sheet 3 Filed March 2, 1960 Eva/v1 TAP 64 OFF/6.2

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United States Patent Ofitice 3,058,242 Patented Oct. 16, 1962 This is a continuation-in-part of application Serial Number 624,624 filed November 27, 1956, by Frank J. Ocnaschek for Control System for Earth Moving Machine, now abandoned.

This invention relates to the automatic control of earth moving machines and more particularly to such automatic controls for accurately positioning the cutting blade of such earth moving machines in a preselected plane.

With the advent of the extensive road building program of recent years, automatic and accurate control of earth moving machines has become a matter of prime economic importance. More specifically, it has become quite important to be able to cut grades with a prescribed accuracy and in a minimum of time. This invention provides a novel automatic control system for accurately positioning the blade of an earth moving machine in a preselected plane so that a predetermined prescribed cut may be made in the earths surface.

It is an object of this invention to provide a novel automatic control system for controlling the blade of an earth moving machine to accurately contour the earths surface.

Another purpose of this invention is to provide a novel control system which is operable to control the elevation of the blade of an earth moving machine within close tolerances.

A further object of this invention is to provide an accurate control system for the blade of an earth moving machine wherein no part of such control system is external to the earth moving machine.

An additional object of the invention is to provide an economical, yet accurate, control system for controlling the position of the cutting blade of an earth moving machine with respect to a predetermined plane.

A fifth aim of the invention is the improvement of tractor blade control devices generally.

These and other objects of this invention will become more apparent from the following description thereof when read in conjunction with the drawings in which:

FIG. 1 is a side representation of an earth moving machine, or tractor, and its blade with relation to a predetermined plane;

FIG. 2 is a combination block diagram and schematic representation of one embodiment of a system for developing the control voltage signal employed to control the height of the blade;

FIG. 3 is a schematic representation of one embodiment of a sine generator;

FIG. 4 is a schematic representation of one of the blocks shown in FIG. 2;

FIG. 5 is a detailed schematic diagram of a block shown in FIG. 2; and

FIG. 6 is a perspective view of the tractor blade and the means for utilizing the control signal developed by the structure of FIG. 2.

Referring now to FIG. 1, it is apparent that in order to control the blade 10 of the earth moving machine or tractor 11 with respect to the reference plane 12, several factors must be accurately determined. These factors are the height H of the tractor, the pitch angle 0 of the tractor, and the angle of the blade 10 with respect to the tractor. The position of the blade 10 is to be 2 determined without the use of any apparatus external to the tractor 11.

In FIG. 1, the distance of the cutting edge of the blade 10 from the reference plane 12 is depicted as distance D. The distance D is equal to the distance H of the tractor from the reference plane 12 plus the distance R from the tractor to the cutting edge times the quantity sin (6+). The complete equation for D is thus,

By accurately determining and controlling the value of D the cutting of the earths surface by the tractor blade. It) will, of course, be accurately controlled.

In Equation 1 the distance H can be determined by integrating the vertical distance traveled by the tractor if the path of the tractor is described by the equation H:f(L), where L is the distance traveled along the reference plane 12. Likewise, the slope of the path of the tractor can be referred to as a function of 0 where It can be seen from the above equations that the ver-- tical distance traveled by the tractor can be defined for any given angle of 0 as H :L tan (0).

Thus,

H=d1 tan m 0 may be instantaneously determined from a vertical gyro 61 (FIG. 2) which is mounted upon the tractor frame and the gyro synchro takeoif 21. The integration necessary may be performed by a standard ball, disc, and roller (DBR) integrator such as that shown in FIG. 3. The integrator includes the disc 31, the balls 32, and the roller 33. The pertinent relations of the disc, ball and roller integrator are stated in the following equation:

a =a ky where a :angular position of roller 33 output a =angular position of input shaft 34 y=contro1 rod 35 displacement lc=a constant dependent upon diameter of output roller In the structure of FIG. 3 the shaft 34, which turns the disc 31, is in turn driven by suitable means from within the tractor so as to have an angular rotation a proportional to the distance traveled by the tractor. Such suitable means can be gear means (not specifically shown) connected to the tractor tread drive. The output signal of the structure of FIG. 3 appears as an angular rotation of a of the roller 33. In the operation of the device of FIG. 3 the control rod 35 is displaced either to the left or to the right in the drawing, depending on changes in the angle 0, which changes are caused by the action of the vertical gyro 61 of FIG. 2. The takeoff 21 is driven by the shaft 62 (FIG. 2) which is also employed to drive the shaft 63 of FIG. 4 as will be discussed later. When the rod 35 is moved to the right from the position shown in FIG. 3, the balls 32 are moved further out on the periphery of the disk 31 which results in a greater angular rotation of the balls 32 (for a given angular rotation of the disc 31). Consequently the roller 33 will experience a correspondingly greater rotation, which in turn will indicate a greater change in the vertical position of the tractor. It is to be noted that disc 31 drives the upper ball of balls 32 which in turn drives the lower ball, the lower ball then driving the roller 33. Should the rod 35 cause the balls 32 to move to the left of the shaft 34 in FIG. 3, the direction of rotation of the balls 32 will be reversed and will record From FIG. 3 it can be seen that y is proportional to the sin of 0, or

The quantity a; is proportional to L, or a =CL. Substituting the values of y and a in the difierential Equation 5, the following equation results:

g i'd kNdH dt dt dL where C, k and N are constants.

As indicated hereinbefore it is possible to make a proportional to L by using a fifth Wheel on the earth moving machine with a mechanical takeoff therefrom.

Since L and t are independent variables, a new equation may be written:

da =CkN dH (7) If both sides of this equation are integrated, a =FH Where F=CkN, which is a constant showing that the angular position n of the output roller is proportional to the vertical distance traveled, H.

In Equation 3 there appears the expression tan 1 Because the angle 0 is usually quite small it has been found possible to employ a sine generator, in lieu of a tangent generator, since for small values of 0 the sine function and the tangent function are substantially equal. Such a sine generator is represented by the block 22 of FIG. 2 and is shown in detail in FIG. 3. The block 36 of FIG. 2 represents the disc 31, the balls 32, and the roller 33 of FIG. 3. In FIG. 3 the rod 35 is connected to a point 105 on the arm 56 of length N which is mounted on the disc 22 which in turn rotates about the axis 55. The axis 55' is driven by suitable means (not shown), from the shaft 62 of FIG. 2 and maintains the arm 56 at an angle 0 from the vertical position. The lateral displacement of the rod 35 is represented by Y=N sin 6 as discussed above. It is to be understood that if 0 should be large enough so that the sine and tangent functions are appreciably different, then a true tangent generator, of which there are many in the art, instead of a sine generator should be employed.

At this time the specific means by which the axis 55' is driven from the shaft 62 of FIG. 2 will be discussed now in more detail. A vertical gyro 61 located on the tractor responds to movement-s about the vertical axis to drive shaft 62, which in turn drives a rotor, not shown specifically, but which is included within the block 118 of FIG. 2 Such rotor is energized by an A.C. voltage such as voltage source 67 of FIG. 2, and functions to induce a spatially oriented voltage in a Y three winding stator, which stator also is included in the block 118, but not specifically shown. The aforementioned stator may be of the same configuration as the stator 117 and have its end terminals connected to the end terminals of the stator 117. Thus, the spatially oriented field is reproduced in the stator 117. That component of the spatially oriented voltage in the stator 117 which is parallel with the rotor winding 640 will induce a voltage in the rotor 640. Such voltage is amplified by servo amplifier 115, the output of which functions to energize the servo motor 116 which drives the rotor 640 to a null position. Thus, the angular position of the shaft 55 will always come to rest in the same angular position as the shaft 62.

Referring again to the structure of FIG. 3, the transverse motion Y of the sine generator is applied to the standard disc, ball, roller integrator 36 shown in detail in FIG. 3 to produce an output signal a which is the angular rotation of the roller 33. Referring now to FIG. 2 the output roller 33 of the DBR integrator 36 drives the tap 64 of a voltage divider 25 to vary the A.C. voltage supplied to the voltage adder 23 in accordance with the amount of rotation of the roller 33.

The A.C. voltage supplied to the voltage adder 23 from resistor 25 is proportional to H. It is now necessary to generate a voltage proportional to R sin (6-|-). Such a voltage proportional to R sin (fl-l-qs) may be produced by the circuit shown in FIG. 4. The output of the gyro transmitter 41 which comprises stator 66 and rotor 53 is a synchronous takeoff from vertical gyro 61 of FIG. 2. A.C. voltage source 67 is employed to energize the rotor 53 which is driven by the rotating shaft 62 of FIG. 2 and which has an angular rotation equal to 0. In response to the rotation of the rotor 53 there will be produced a corresponding spatially oriented field in the stator 66. The spatially oriented field is reproduced in the three winding stator 50 of the differential transformer 42 which also includes a rotatable element 51 having three coils connected in Y arrangement. The field induced in the rotor 51 can thus be reproduced in the stator 43 of the control transformer and can be spatially oriented in the same manner as the field in stator 66.

However, it is desirable to have the spatial orientation of the field in the stator 43 with respect to the vertical be equal to the angle 0:1 5 rather than just the angle 6. The angle 0 is added to the spatial orientation of the field by means of the differential transformer 42. More specifically, by suitable coupling means, the shaft 92 of FIG. 6 is made to drive the shaft 96 of the differential. Thus the element 51 is rotated through an angle 6 which is equal to the angle that the blade of the tractor makes with the longitudinal axis of the tractor. It can be seen from the drawing that the resultant signal produced in the stator 43 of the control transformer consequently will have a spatial orientation representative of the sum of the angles 8 and The magnitude of the voltage induced in the element 57 of the control transformer will thus be proportional to the sine of the angle (6+). Since R (see FIG. 1) is a constant, the voltage produced across the element 57 will be proportional to R sin (0+q5). and will be representative of the distance D-H (FIG. 1).

It is now necessary to add the voltage representative of H and the voltage representative of R sin (0+q5) to generate a reference voltage which is proportional to the distance D of the cutting edge of the blade from the reference plane 12. This voltage may be produced by adding the voltages generated in the circuit of FIG. 4 and the voltage appearing across the tapped portion of the resistor 25 of FIG. 2 in any well-known voltage adding system 23. The voltage from the adder 23 may then be used as a control voltage for control unit 24 for positioning the blade of the earth moving machine. This control voltage, which is proportional to D, will function to maintain the cutting blade 10 at a certain predetermined distance D from the reference plane 12. The control unit 24, which is shown in detail in FIGURE 6, will be discussed later herein.

In FIGURE 5, there is shown a specific form of a voltage adding means which may be employed in this invention. Essentially, the voltage adding system utilizes two isolating resistors 63 and 66 to apply the signal to transformer 65. The output of transformer 65 is a combined signal composed of a voltage representative of the distance H from resistor 25 in FIGURE 2 and a voltage representative of R sin (6+) from winding element 57 of FIGURE 4. The combined voltage is therefore proportional to the vertical distance D shown in FIGURE '1. The phase of the signal is employed to determine if the distance D is above or below the reference plane 12, and the magnitude the relative distance from the reference plane 12.

From transformer 65, the signal passes through a phase detector composed of diodes 62 and 63, tapped resistor 6 and a source of reference voltage 76. The output signal appearing at 78, therefore, is a DC. signal whose polarity is representative of whether distance D is above or below reference plane 12, and whose magnitude is representative of the distance from the reference plane 12.

The voltage at 78 representative of distance D is then applied to a servo system employed to position the blade '1 to some position corresponding to the magnitude of the voltage at 73. In other words, if the voltage present on the conductor 78 indicates that the cutting edge of blade 16' is above the desired height, then the voltage on 78 would cause the servo system to lower the blade a desired distance in order that future cutting action would decrease the distance D. Conversely if the voltage or conductor 78 indicates that the cutting edge of the blade 19' is below the desired height, then the voltage or conductor 78 would cause the servo system to raise the blade a predetermined distance. More specifically the servo system error signal appearing on conductor 78 also appears on the conductor 89 in a somewhat reduced magnitude and causes the hydraulic control valve 84 to open, which in turn causes the blade 10 to move either up or down, depending on the polarity of the error signal.

The potentiometer 105 comprising resistor 68, tap 1M), and batteries 1G1 and 102 constitutes a rate feedback structure, when the blade 1% moves either up or down, the tap 109, which is mechanically coupled to the blade 10', will move in a direction so as to diminish the error signal, thus preventing large movements of the blade 10 which otherwise could be of a magnitude as to dig deeply enough into the ground to stall or even upset the tractor.

Consider a specific situation. Assume 5 and to be zero and asume that the potential of the signal suddenly appearing on conductor 80 is positive and calls for a four inch drop of the tractor blade 16' (in the absence of any effect from the potentiometer 105). As the blade begins to lower, however, the potential of the tap 100 will become more negative, thus in effect making the signal on lead 8t positive and calling for a blade drop of less than four inches. The ultimate drop of the blade will be, perhaps, of the order of two inches, depending upon the specific design parameters of the circuit. As the tractor moves forward and over the newly graded surface the tractor itself will be lowered, thus initiating an error signal calling for a slight raising of the blade, in an amount of the order perhaps, of one inch so that the blade is now but an inch below its original setting with respect to the tractor but the position of the tractor is two inches below its original setting. Thus the blade is three inches below its original absolute setting. As the tractor moves farther along its path its position will be lowered even further. The eventual position of both the tractor and the blade will be four inches below their original positions (assuming that both and 0 were zero when the original signal calling for a four inch drop of the blade occurred).

It is to be noted that when the angles and 0 (see FIG- URE l) are zero and when the distance H is zero the output signal appearing on lead 7 8 is zero and the voltage appearing tap 1% is at zero (or ground) potential. Under these conditions the potential appearing on conductor Si) is ground. Such conditions represent the normal conditions when the tractor is grading properly. Of course, it is to be realized that the reference plane 12 could be the plane at which grading is to occur. The reference plane can be above, below, or at the level to be graded. The circuit parameters must be designed accordingly.

Now, if it were only desired to maintain the blade 10 at a constant distance above the reference plane 12 the struc ture described so far is sufficient to accomplish such a purpose. However, it may be desirable to cause the height of the blade to vary in a predetermined manner in accordance with the forward progress of the tractor. To enable this function there is provided a cam arrangement including cam 97 having a shaft 98 which is mounted on the frame of the tractor 11 and which is driven by an appropriate means off the main drive of'the tractor, such as by the fifth wheel means mentioned hereinbefore. It will be apparent that gear reduction means are required between the main drive and the cam 97 so that a complete rotation of the cam 97 might represent several hundred feet or more of forward travel of the tractor. The cam 97 is mechanically coupled to the tap 110 of potentiometer 111 and functions to change the magnitude of the potential of tap 110. Such a change in potential will cause the servo system to again adjust the voltage on conductor to zero, and in the process thereof, positioning the blade 10 to the desired cutting position. By properly forming the shape of the cam 97 it will be apparent that the height of the blade 10 at any point in a path of the tractor 11 can be varied in accordance with a predetermined function. it is to be noted that the invention herein shown and described is but a preferred embodiment thereof and that various changes and modifications may be made therein without departing from the spirit or scope thereof.

1 claim:

1. An integrally mounted control system on an earth moving machine having a cutting blade attached thereto including means for generating signal voltages proportional to the sine of the sum of a plurality of angles including at least the angle of said earth moving machine with respect to a fixed reference plane and the angle of said blade with respect to said earth moving machine, means for generating signal voltages proportional to the distance of said earth moving machine from said fixed reference plane, means for adding said signal voltages to obtain a control voltage output signal, and means responsive to said control voltage output signal for positioning said cutting blade of said earth moving machine to a desired height with respect to said fixed reference plane.

2. An integrally mounted control system on an earth moving machine having a cutting blade affixed thereto including means for generating a first signal voltage proportional to the sine of the sum of a pair of angles including the angle of said earth moving machine with respect to a fixed reference plane and the angle of said blade with respect to said earth moving machine, said means including a stable reference plane genenating means and means for generating a second signal proportional to the angle between said reference plane and said earth moving machine, means for generating a third signal proportional to the forward motion of the earth moving machine, means responsive to said second signal and said third signal for generating a signal v-otlage proportional to the distance of an earth moving machine from the fixed reference plane, means for combining said signal voltages to obtain a control voltage output signal, and means responsive to said control voltage output signal for positioning said blade of said earth moving machine to cut the earths surface in a desired contour.

3. An integrally mounted control system on an earth moving machine having a cutting blade affixed thereto including first means for generating a first control signal proportional to the sine of the sum of a pair of variable angles including the angle of said earth moving machine with respect to a stable reference plane and the angle of said blade with respect to said earth moving machine, said signal voltage generating first means including means for generating a stable reference plane, means for generating a second control signal proportional to the instantaneous angle between said earth moving machine and said stable reference plane, means including a differential rotor and stator circuit for generating an output tional to the distance of said earth moving machine from said fixed reference plane, means for adding said first control signal and said fourth control signal to obtain an output control voltage, and means responsive to said last mentioned output control voltage for positioning said blade of said earth moving machine to cut the earths surface in a predetermined contour.

4. An integrally mounted control system on an earth moving machine having a cutting blade affixed thereto including first means for generatihg a first signal voltage proportional to the sine of the sum of the angle between said earth moving machine and a stable reference plane and the angle between said blade of said earth moving machine and said earth moving machine, said first means comprising a fixed reference plane generating means, second means for generating a second signal voltage proportional to the distance of said earth moving machine from the fixed reference plane including means for generating a second signal voltage proportional to the sine of the variable angle between said fixed reference plane and the actual plane of said earth moving machine and means for indicating the lineal travel of said earth moving machine, means for adding said first and second signal voltages to obtain a control voltage, and means responsive to said control voltage for positioning said blade of said earth moving machine to cut the earths surface in a predetermined contour.

5. An integrally mounted control system on an earth moving machine having a cutting blade aifixed thereto including first means for generating a first signal voltage proportional to the sine of the sum of the variable angle between said earth moving machine and a stable reference plane and the variable angle between said blade of said earth moving machine and said earth moving machine, said first means comprising means for establishing a fixed reference plane, means for generating a second signal voltage proportional to the distance of said earth moving machine from said fixed reference plane including means for generating a signal voltage which varies proportionally to the sine of the variable angle between said fixed reference plane and the actual plane of said earth moving machine and means for integrating the instantaneous signal voltage proportional to said sine of said variable angle with respect to the distance of said earth moving machine along said fixed reference plane, means for adding said first and second signal voltages to obtain a control voltage, and control means responsive to said control voltage for positioning said blade of said earth moving machine to cut the earths surface in a predetermined contour.

6. An integrally mounted control system on an earth moving machine having a cutting blade affixed thereto including means for generating a stable reference plane, means for generating a first signal voltage proportional to the sine of the sum of the instantaneously variable angle between said earth moving machine and said stable reference plane and the instantaneously variable angle between said blade :and said earth moving machine, means for generating signal voltages proportional to the distance of said earth moving machine from a fixed reference plane including said means for generating a fixed reference plane and means for generating a second signal voltage proportional to the sine of the variable angle between said fixed reference plane and the actual plane of said earth moving machine and integration means for integrating the signal voltages proportional to said sine of said variable angle with respect to the travel of said earth moving machine along said fixed reference plane, and means for generating a third signal voltage proportional to the output signal of said integration means, means for adding said signal voltage from said sine generating means and said third signal voltage to obtain an output control voltage, and means responsive to said output control voltage for positioning said blade of said earth moving machine to cut the earths surface in a predetermined contour.

7. A control system entirely mounted on a tractor type device having a pivotal blade mounted thereon and constructed to control the elevation of said blade, said control system comprising means for establishing a constant reference plane, means for producing a signal indication of the deviation of the actual slope of said tractor from a desired slope with respect to said reierence plane, means for integrating the product of lineal travel of the tractor times the sine of the angle between said actual slope and said desired slope to produce an output signal representative of the cumulative record of the elevation of the tractor, means including differential means for producing a signal voltage proportional to the sine of the sum of the angle between said actual slope and said desired slope and the angle between said actual slope and said blade, means responsive to said output signal representative of said cumulative record and said signal voltage to produce a resultant output signal whose magnitude is representative of the elevation of said blade, and means constructed to respond to said output signal to adjust said blade to a predetermined elevation.

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